Solid bowl centrifugal separator

ABSTRACT

A centrifugal separator for the removal of solids from slurry. A high-speed bowl which rotates about a vertical axis is centrally fed with slurry in its upper region. A circular ceiling plate above the level of slurry feed establishes with the cylindrical upper rim section of the bowl a narrow annulus which becomes sealed with sludge as the solid constituents build up in the vicinity thereof and a series of plows advance slowly around the annulus and through the sludge seal and serve to elevate the sludge above the ceiling plate and into the path of a series of rotatable buckets. The latter orbit at a slightly increased speed around the bowl interior and in connection with rotation thereof assume outside ecliptic positions where they scoop wads of sludge from the sludge seal. Such buckets also in connection with rotation thereof assume inside ecliptic positions where their directional relationship is reversed so that centrifugal force dislodges the wads and causes them to be flung radially outwards over the rim of the bowl. The liquid constituent of the slurry is forced outwardly through an outlet in the bowl bottom wall.

United States Peck et al.

atet [191 1 SOLll) BOWL CENTRIFUGAL SEPARATOR [76] Inventors: William H. Peck, 2508 Omaha,

Pittsburg, Kans. 66762; Samuel A. Collier, 7029OE. Avenue, Tulsa, Okla. 74112 22 Filed: Mar. 15,1973

211 App]. No.: 341,527

[52] US. Cl 233/7, 233/22, 233/25, 233/32, 233/46 [51] Int. Cl B04l) 1/00 [58] Field of Search 233/3, 7, 21, 22, 23 R, 233/24, 25, 26, 27, 28, 46, 32; 210/325, 370, 380, 385

[56] References Cited UNITED STATES PATENTS 2,796,990 6/1957 Peck 210/370 3,394,879 7/1968 3,402,821 9/1968 3,627,138 12/1971 Peck 210/325 Primary Examiner-George l-l. Krizmanich Attorney, Agent, or Firm-Norman H. Gerlach A centrifugal separator for the removal of solids from slurry. A high-speed bowl which rotates about a vertical axis is centrally fed with slurry in its upper region. A circular ceiling plate above the level of slurry feed establishes with the cylindrical upper rim section of the bowl a narrow annulus which becomes sealed with sludge as the solid constituents build up in the vicinity thereof and a series of plows advance slowly around the annulus and through the sludge seal and serve to elevate the sludge above the ceiling plate and into the path of a series of rotatable buckets. The latter orbit at a slightly increased speed around the bowl interior and in connection with rotation thereof assume outside ecliptic positions where they scoop wads of sludge from the sludge seal. Such buckets also in connection with rotation thereof assume inside ecliptic positions where their directional relationship is reversed so that centrifugal force dislodges the wads and causes them to be flung radially outwards over the rim of the bowl. The liquid constituent of the slurry is forced outwardly through an outlet in the bowl bottom wall.

43 Claims, 17 Drawing Figures PAIENIED Aum 31914 sum 5 or 7 FIG. 6

SOLID BOWL CENTRIFUGAL SEPARATOR PERTINENT PRIOR ART (United States Patents) 2,796,990 Class 2l0-370 The present invention relates generally to a centrifugal separator and has particular reference to a novel separator of the type which is employed for separating solids from a liquid (slurry) as, for example, in the drying of pulverized coal, sand, and other granular materials, in the pelletizing of minerals such as iron ore, or in sewage treatment.

The particular centrifugal separator of the present invention is designed as an improvement over previously designed centrifugal separators for the same purpose as well as the particular separators which are disclosed in US. Pat. No. 3,402,821, granted on Sept. 24, 1968 and US. Pat. No. 3,627,138, granted on Dec. 14, 1971, each of two such patents being entitled CEN- TRIFUGAL SEPARATOR.

In the centrifugal separator of aforementioned US. Pat. No. 3,402,821, slurry is fed directly into a series of circumferentially spaced revolving baskets which orbit about the central axis of a carrier and have curved or arcuate filter screens which assume inside and outside ecliptic positions with respect to the axes of revolution of the baskets and the axis of rotation of the carrier. In their outside ecliptic positions, the screens pass liquid to associated collector walls from which the liquid is drawn off by gravity. In the inside ecliptic positions of screens, the particles which adhere to the screens and ordinarily would tend to clog the same are flung free of the screens in order to produce a self-cleaning action. At a position in between their ecliptic positions, the

screens assume radial positions so that the collected solids thereon slide therefrom endwise and are flung outwardly of the carrier to a point of discharge.

It has been found that while a centrifugal separator such as has briefly been described above is entirely satisfactory for certain slurries, when it is applied to slurries having solids smaller than 325 mesh, an excess amount of the solid type material passes through the screens and is discharged with the effluent with the result that the latter is not clear liquid.

In the centrifugal separator of later-issued US. Pat.

vNo. 3,627,138, a similar structure is employed, but instead of employing orbiting perforated baskets, solid wall-type vanes which curve in involute fashion are used. In the various outside ecliptic positions of each vane, the vane functions as a solid wall centrifuge for a brief moment so that the heavier solids settle against the vane while clear liquid remains at regions remote from the vanes. Small discharge openings leading from these regions serve to draw off the clear liquid while the less heavy solids slide sidewise from the vanes when the latter assume positions in between their inside and their outside ecliptic positions. These semi-solids are drawn off through similar small discharge openings near the ends of the vanes. When the vanes assume their inside ecliptic positions, their direction of rotation is reversed and centrifugal force acting on the heavy solid particles dislodges them from the vanes and places them in the gravitational field of the carrier where they are flung radially from the latter.

While the particular centrifugal separator of the last mentioned patent similarly serves its intended purpose with reasonable efficiency, its principal limitation is that the mass which is involved in the orbiting rotational baskets causes a practical upper force limit of the order of 1,000 Us Most small, low specific gravity particles require forces in excess of 1,000 US to bring about good separation. The present invention is designed to supplement the separator of US. Pat. No. 3,402,821 in that it will receive the effluent from the latter and recover the solids and give a clear liquid. It further supplements and eliminates the limitations of the separator of US. Pat. No. 3,627,138 in that it is not limited in its G force capability range.

The present invention is designed to overcome all of the above-noted limitations that are attendant upon the construction and use of both of the aforementioned patented separators and toward this end the invention contemplates the provision of a novel and improved centrifugal separator which employs a separator bowl which is solid, rotates about a central vertical axis at an extremely high speed, and is fed with slurry in its central upper region so that the solid particles of the slurry progress radially outwardly of the bowl under the influence of centrifugal force. A circular deck plate below the point of slurry entry or introduction terminates short of the periphery or rim section of the bowl and establishes a wide annulus through which liquid first flows downwards into the lower central region of the bowl and then outwards through one or more liquid outlets. A circular ceiling plate above the point of slurry feed and also the deck plate also terminates short of the bowl periphery and establishes a second and narrow annulus of such restricted area that it blocks the free passage of slurry upwardly therethrough and thus establishes an annular blockage or ring of dense sludge (herein referred to as sludge seal) in the peripheral or rim region of the bowl. Above this ceiling plate and within the confines of the bowl in the upper region thereof, a rotatable carriage in concentric relationship with the bowl rotates at a speed which is slightly higher than that of the bowl and carries a series of plows at its periphery which traverse the sludge seal and forces increments (wads) of the sludge upwardly through the narrow annulus and into the path of movement of a plurality of orbiting buckets. The latter, by means of planetary gearing, travel with the carriage in planetary fshion so that they assume outside and inside ecliptic positions with respect to the axis of rotation of the bowl. In their outside ecliptic positions, the buckets traverse the sludge seal and scoop small quantities (wads) of sludge and carry them to inside ecliptic positions where the buckets become reversed as to their orientation with the result that their open sides face away from the axis of rotation of the bowl. In thus moving toward their inside ecliptic positions, the buckets encounter a cam which raises them to a higher elevation above the level of the upper edge of the bowl and the wads of sludge within the buckets are thus constrained to be flung outwardly by the centrifugal force over the rim of the bowl to a region of discharge. In this manner, solids are separated from the liquid without any intermediate gradation of semi-solids or semi-liquids. Since there are no perforate screens or small passages involved, clogging of discharge apertures or openings by solids is avoided, as also is the use of water or other liquid under pressure for flushing or purging purposes. The provision of a centrifugal separator such as has briefly been outlined above constitutes the principal object of the present invention.

The provision of a centrifugal separator which is relatively compact and, therefore, consumes but little floor space; one which is capable of ease of assembly and dismantlement for purposes of inspection, repair, or replacement of parts; one which is rugged and durable and, therefore, will withstand rough usage; one which is comprised of a minimum number of moving parts and, therefore, is unlikely to get out of order; one which is centrifugally balanced for smooth and relatively silent operation; and one which, otherwise, is well-adapted to perform the services required of it, are further desirable features which have been borne in mind in the production and development of the present invention.

Other objects and advantages of the invention, not at this time enumerated, will become readily apparent as the nature of the invention is better understood from a consideration of the following detailed description.

The invention consists in the several novel features which are hereinafter set forth and are more particularly defined by the claims at the conclusion hereof.

In the accompanying seven sheets of drawings forming a pair of this specification, one exemplary embodiment of the invention is shown.

IN THESE DRAWINGS:

FIG. I is a side elevational view of a solid bowl centrifugal separator embodying the principles of the present invention, portions of the separator frameworktype casing being broken away in order more clearly to reveal the nature of the invention;

FIG. 2 is a vertical sectional view taken on the line 2-2 of FIG. 1;

FIG. 3 is a top plan view of the structure which is shown in FIG. 1;

FIG. 4 is an enlarged developed 90 quarter section taken substantially on the line 4-4 of FIG. 3 and in the directions indicated by the arrows;

FIG. 5 is a fragmentary vertical sectional view taken on the line 55 of FIG. 3;

FIG. 6 is an enlarged horizontal sectional view taken substantially on the line 6-6 of FIG. 5;

FIG. 7 is an enlarged horizontal sectional view taken on the line 7-7 of FIG. 1, portions of the separator framework being omitted in the interest of clarity;

FIG. 8 is an enlarged detail sectional view taken substantially on the vertical line 77 of FIG. 4 and-illustrating specifically the nature of a bucketactuating cam which is employed in connection with the present invention;

FIG. 9 is a side elevational view of the structure which is shown in FIG. 8;

FIG. 10 is a perspective view of one of the two rotatable orbiting bucket carriers which are employed in connection with the invention;

FIG. 11 is a perspective view, largely schematic in its representation, illustrating the nature of the power trains by means of which the separator bowl and bucketsupporting carriage are rotated respectively at slightly different rates of speed, and also illustrating the planetary gearing by means of which orbital motion is imparted to the bucket turntables;

FIG. 12 is a fragmentary plan view looking downwardly in the peripheral region of one of the bucket turntables and illustrating the manner in which each bucket which is associated with such carriage initially engages a bucketdeflecting cam by means of which the bucket is swung to a raised sludge-discharging position;

BRIEF DESCRIPTION OF SEPARATOR Referring now to the drawings and in particular to 1 FIGS. 1 and 2, considered in conjunction with the schematic disclosure of FIG. 10, briefly, the solid bowl separator of the present invention embodies a fixed framework the nature of which will be described in detail presently. Such framework serves to support a fixed annular liquid-collecting and discharge pan 10. Above this pan there is rotatably supported a high-speed separator bowl 12 having downwardly and outwardly extending liquid discharge outlets 14 which open into the annular pan 10. Slurry which is continuously introduced into the central region of the bowl 12, as hereinafter described in detail, is flung radially outwardly under the influence of centrifugal force and passes over a lower circular deck plate 16-toward the rim or peripheral region of the bowl where the solid constituents thereof impact against such region and establish a ring of relatively dense sludge which extends completely around the inner surface of the rim or peripheral region of the bowl while the liquid constituent (water ordinarily) of the slurry flows downwardly by gravity over the peripheral edge of the deck plate 16 and then via the outlets 14 into the pan 10 from whence it is discharged through a downwardly facing liquid discharge outlet 18 in the bottom wall of the pan 10. This ring of dense sludge will vary in size and density, depending, of course, upon the character of the liquid material (slurry) undergoing treatment, i.e., its specific gravity, the soIid-to-liquid ratio of the material, the rate of bowl rotation, and many other factors too numerous to mention. The peripheral area in which such sludge collects or builds up may best be visualized by reference to FIG.

' 4 where it is represented by stippling and designated by the legend sludge seal, as well as being designated by the reference numeral 20. I The building up of such a ring of dense sludge is made possible by the provision of an upper ceiling plate order of 3,000 rpm. and, thus, the solid constituents of the slurry are impaced with relatively high centrifugal force against the peripheral region of the bowl 12, while the liquid constituent of the slurry flows downwardly over the circular peripheral edge of the deck plate 16 as shown by the curve arrows in FIG. 4 and collects in the central lower region of the bowl where it is then discharged downwards and outwards through the liquid discharge outlets 14.

Separation and removal of solids from the slurry is predicated upon a novel means of handling the sludge which, as previously stated, collects in the form of an annulus or ring in the peripheral region of the bowl. According to the present invention, this sludge which ordinarily is of mud-like consistency is initially allowed to build up in the peripheral region of the bowl until it establishes the aforementioned sludge seal 20 between the outer circular edge of the ceiling plate 22 and the adjacent surrounding peripheral region of the bowl 12. As soon as this sludge seal 20 has been established, there come into play means for continuously withdrawing it at a rate substantially commensurate with its rate of deposition at the periphery of the bowl, such means taking the form of two annular series of scoop-like buckets 30.

The series of buckets 30, as will be made clear presently, are revolvable in orbital fashion about the vertical axis of the central shaft 26 and the individual buckets of each series are movable in circumferential fashion about respective vertical axes which, themselves, orbit about the shaft 26 as indicated by the curved or arcuate full line arrows at the right-hand side of FIG. 3 of the drawings.

The two series of scoop-line buckets 30 are supported on a rotatable bucket carriage 32 which rotates about the vertical axis of the central shaft 26. The individual buckets 30 of each annular series are mounted on a rotatable bucket turntable 34 (see FIG. 10) which is rotatable on the carriage 32 and also revolves bodily about the vertical axis of the central shaft 26. The shaft 26, the bucket carriage 32, and each bucket turntable 34 thus assume a planetary sun-earth-moon relationship. As will be described in greater detail hereafter, the rate of rotation of the bucket carriage 32 about the central shaft 26 is slightly greater than the rate of rotation of said central shaft and the bowl 12 which it supports, an exemplary speed of rotation for the shaft and bowl being on the order of 3,000 rpm. as compared to 3,002 rpm. for the bucket carriage 32. Thus each annular series of buckets 30, as exemplified by its respective turntable 34, walks so to speak around the bucket carriage 32 at a rate of 2 rpm., although it revolves about the central shaft 26 at an extremely high speed, i.e., 3,002 rpm. By the same token, each bucket tumtable 34 rotates on the bucket carriage 32 at a relatively slow speed.

Still referring to FIGS. 1 to 4, inclusive, and also FIG. 10, the buckets 30 which are disposed in circumferentially spaced relationship on their respective bucket turntables 34 are individually pivoted on such turntables for swinging movement about respective hori zontal axes between lowered positions corresponding to the position of one of the buckets as shown near the upper left-hand side of F IG. 4, and a raised position corresponding to the position of another bucketwhich is shown substantially mid-way between the central shaft 26 and the rim or periphery of the deck plate 16 in FIG. 4.

Successive raising movement of the buckets 30 is effected under the control of cam surfaces 40 which are movable with the carriage 32, while successive lowering of the buckets is effected under the control of cam surfaces 41 which also are movable with the carriage 32.

Since each bucket turntable 34 rotates about its own vertical axis at a rate of approximately 2 rpm. as previously described, the various buckets which are peripherally mounted thereon sweep or swing into and out of the peripheral region of the bowl 12 at a relatively slow rate of travel for sludgescooping purposes. Circumferentially spaced, sludgeelevating plows 42 are carried on the periphery of the bucket carriage 32 and these plows are positioned so as to loosen the sludge mass or seal and carry it upwardly above the level of the ceiling plate 22, thus moving it into the general level of the bucket turntables 34 where it is picked up by the buckets 30 at such time as they are in their outside ecliptic position. As the buckets 30 move or swing toward their inside ecliptic positions they encounter the cam surfaces 40 which raise them progressively and, at such time as the sludge-filled buckets arrive at their inside ecliptic position, the direction of the buckets has become reversed so that the contents of the buckets are flung radially outwardly of the carriage 32 by centrifugal force due to the extremely high orbital speed of the turntables 34 and such contents (wads of sludge) are caused to impact against a slowly rotating cylindrical outer solids-gathering apron 44 (see FIG. 2) from whence they are loosened by a series of fixed scraper blades 46 (see FIG. 3) and allowed to fall by gravity from the rotating apron 44. The buckets 30 in returning to their outside ecliptic positions encounter the cam surfaces 41 which restore them to their lowered positions.

THE SEPARATOR FRAMEWORK AND OTHER FIXED PARTS The framework of the present centrifugal separator is best illustrated in FIGS. 1, 2 and 3 of the drawings and comprises a base structure 50 which is formed of channel members and consists of front and rear channels 52 and 54 (see FIG. 3) and longitudinally extending channels 56 and 58, the latter being welded at their ends to the channels 52 and 54. As shown in the drawings, the base structure 50 supports a pair of front upright angle pieces 60 the upper ends of which serve to support the forward region of the aforementioned annular liquid-discharge pan 10. A pair of wide channel members 62 (see FIG. 1) projects vertically upwards from the longitudinally extending channels 56 and 58 of the base structure, while a pair of longitudinally extending pan-supporting plates 64 extends between the channel members 62 and the two upright angle pieces 60 on opposite sides of the framework and serves to support the rear region of said pan 10.

The wide channel members 62 project above the level of the separator bowl l2 and the upper end regions of such members serve to support a superstructure 66 (see FIGS. 1, 2 and 3), such superstructure consisting of a relatively short horizontal top plate 68, and a relatively long horizontal bottom plate 70, and a pair of side plates 72 and 74. The top and bottom plates 68 and 70 project forwardly from the upper end regions of two wide channel members 62 and have their rear portions welded to said upper end regions. Additional angle pieces 76 and 78 project vertically upwardly from the channel 56 and 58 and afford a support for an adjustable motor mount 80, the nature and function of which will be made clear subsequently. A horizontal transverse-extending frame member 82 (see FIGS. 1 and 3) extends between, and is suitably fixedly connected to, the upper central regions of the wide channel members 62 and constitutes a support for a second motor mount 83, the function of which also will be set forth subsequently. Other and minor frame adjuncts, not at this time specified, will be mentioned at such time as an explanation of their relationship to structure undergoing discussion is deemed necessary.

THE LIQUID-COLLECTING AND DISCHARGE PAN The annular liquid-collecting discharge pan 10 directly underlies the bowl 12 and is constructed of heavy gauge sheet metal. It is provided with an annular bottom wall 85 (see FIG. 4) and this, as heretofore indicated, is supported by the upright angle pieces 60 and also by the plates 64. This bottom wall 85 of the pan 10, in combination with an outside cylindrical wall 87 and an inside cylindrical wall 89, defines a circular liquidretaining trough 91 within which the liquid which is discharged from the bowl l2 collects and from which such liquid is discharged downwards through the aforesaid liquid outlet 18. An inturned rim flange 93 on the upper circular edge of the outside cylindrical wall 87 closely hugs the bottom of the separation bowl 12 so that there will be no escape of liquid over the upper rim of the pan I incident to liquid turbulence. The liquid discharge outlet 18 has associated therewith a downspout 95 which may lead to a suitable liquid collection trough or the like (not shown).

THE SEPARATOR BOWL AND ITS SOLIDS WITHDRAWAL MECHANISM (THE BOWL PROPER) As best illustrated in FIGS. 2 and 4 of the drawings,

- the aforementioned separator bowl 12 is centrally supported on the central shaft 26, the bowl being generally semispherical and having curved dished bottom wall 84 which merges with an upper cylindrical rim section 86 of small vertical width, the rim section being provided at its upper edge portion with an outwardly extending rim flange 88. The bottom wall 84 of the bowl has formed in it a central opening 90 through which the central shaft 26 projects. The rim region of the opening seats upon an outwardly extending annular ledge flange 92 which is formed integrally on the central portion of the shaft 26, the bowl being secured to said ledge flange 92 by means of vertical bolts 94 which extend through aligned holes in said rim region of the bowl and the ledge flange.

The aforementioned liquid outlets 14 in the bottom wall 84 of the bowl 12 have associated therewith short discharge tube sections or downspouts 97 which conduct the liquid that is discharged from the bowl 12 below the level of the upper rim region of the annular discharge pan 10 so that such discharged liquid will not be scattered indiscriminately under the influence of centrifugal force incident to the high speed of rotation of the bowl 12. The liquid which is discharged from the downspouts 97 into the interior of the pan 10 is flung radially outwards against the outside cylindrical wall 87 of the pan, collects in the aforementioned annular trough, and is ultimately discharged through the downspout 95.

(THE FIXED BOWL ADJUNCTS) The lower deck plate 16 is of circular disk-like configuration and has formed therethrough a central opening 96 through which the intermediate portion of the central shaft 26 extends. This deck plate, as well as the upper ceiling plate 22, is supported from the bottom wall 84 of the bowl 12 by means of an annular series of circumferentially spaced spacer assemblies 98 including upper and lower spacer sleeves 100 and 102. The lower spacer sleeve 102 of each assembly 98 extends between a fixed inside contoured boss 104 on the bowl bottom wall 84 and the underside of the deck plate 16, while the upper spacer sleeve 100 extends between and serves to space apart the deck plate 16 and ceiling plate 22. Vertically extending bolts 106 are received at their upper ends in tapped holes in the upper ceiling plate 22 and extend through the upper and lower spacer sleeves 100 and 102 of the assemblies 98. The lower ends of the bolts 106 receives thereon nuts 110 which, when tightened, bear against outside contoured bosses 112 on the bowl bottom wall 84. The upper ceiling plate 22 is supported at its central region upon an annular ledge or shoulder 114 which is formed on the intermediate portion of the central shaft 26.

An annular cover plate overlies and is spaced a small distance upwards from the ceiling plate 22 and has its outer marginal portion resting on and secured by vertical bolts 122 to the rim flange 88 on the upper edge portion of the rim section 86 of the bowl 12. It is provided with a relatively large central opening 124 and serves to confine the solids (sludge) which pass upwardly around the periphery of the ceiling plate 22 under the influence of the aforementioned sludge plows 42. This cover plate 120 constitutes an additional fixed bowl adjunct which rotates in unison with the bowl 12. A further fixed bowl adjunct in the form of a sum gear 126 is secured by vertical bolts 128 to the central portion of the ceiling plate 22 and serves to drive the bucket turntables 34 in a manner and for a purpose that will be described presently. The portion of the central drive shaft 26 which passes upwardly through the bowl 12 may be regarded as another bowl adjunct inasmuch as this portion of the shaft affords the means whereby raw or unprocessed slurry is fed centrally into the bowl. Accordingly, this shaft is provided with a longitudinal bore 130 to the lower end of which the slurry is fed. Said lower end of the bore is provided with a conventional slip union 132 (see FIGS. 1 and 2) by means of which it may be connected to a source (not shown) of slurry under pressure. The upper end of the bore 130 communicates with a series of radial passages 134 (see FIG. 4) which lead to the interior of the circular slurry plenum chamber 24 between the slurry deck plate 16 and the ceiling plate 22.

(THE RELATIVELY MOVABLE BOWL ADJ UNCT S) the bucket carriage 32 and such structure as the bowl serves to support, is designed to rotate at a slightly different rotational speed which, for descriptive purposes only, is stated to be 3002 rpm, such preferred rotational speed having been previously mentioned.

The bucket carriage 32 is generally of circular configuration, the over-all diameter thereof being slightly less than that of the rim section 86 of the bowl 12. This carriage involves in its general organization an upper cam plate 140 '(see FIGS. 4, and 6), a lower plowsupporting plate 142 (which hereinafter will be referred to simply as the plow plate), and an intermediate spacer plate 144. The three plates 140, 142 and 144 are secured together for rotation in unison by means of vertically extending clamping bolts 146.

As best shown in FIGS. 4, 5 and of the drawings, each bucket turntable 34 is fixedly secured in coaxial relationship to one of the planet gears 154 by means of an annular series of vertically extending fastening bolts 160. Each turntable 34 and its associated planet gear 154 are sandwiched in or disposed between the upper cam plate 140 and the lower plow plate 142 and are disposed in the general horizontal plane of the spacer plate 144. Each turntable and its associated planet gear 154 are individually rotatable about the axis of a vertically extending central shaft 162 which is surrounded by a bushing 164. The opposite ends of each central shaft 162 are secured in openings 166 and 168 and these are formed respectively in the upper cam plate 140 and the plow plate 142 (see FIG. 5). In addition to being individually rotatable about the axis of its associated central shaft 162, each turntable 34 is capable of orbital movement about said central shaft 26. This orbital movement takes place by reason of the fact that the cam plate 140, and consequently, the entire bucket carriage assembly, is rotated in the same direction as the bowl 12 but at a speed of rotation which is slightly greater than the speed of rotation of the bowl as previously set forth. Thus, as the cam plate 140 of the bucket carriage 34 slowly progresses in a circumferential direction with respect to the sun gear 126, i.e., on the order of 2 rpm., the two planet gears 154 walk around" the circumference of the sun gear 126, thus causing the bucket turntables 34 to rotate about the axes of their respective shafts 162, whereupon the individual buckets 30 will orbit about such shafts and, in doing so, they will exert the desired scooping action on the sludge which has collected in the interior peripheral region of the bowl 12. Because of the sun-earth-moon planetary relationship between the shaft 26, the shafts 162 and the buckets 30, the various buckets (moons) will travel in hypocycloidal paths of movement with respect to space, but insofar as the periphery of the bowl 12 is concerned they will make repeated tangential passes through the sludge ring which collects in the peripheral region of the bowl, each pass being at a point progressively and circumferentially removed from the previous pass. During each bucket pass through the sludge ring, a quantity or wad of the sludge (solids) will be withdrawn from such ring and carried centripetally inwardly of the bowl.

It is obvious that if the various buckets 30 remained at the same elevation, i.e., in the general horizontal plane of the bucket turntables 34 and the spacer plate 144, the mass of sludge which is scraped from the sludge ring at the periphery of the bowl 12 would spill" from the bucket and be flung back into the pcripheral sludge ring by centrifugal force as soon as the individual bucket reversed its direction upon arrival at its inside ecliptic position. Solids separation and removal from the bowl 12 according to the present invention are predicated upon causing each bucket 30 to be swung upwardly under the influence of the aforementioned cam surface 40 as the bucket approaches its inside ecliptic position, thus elevating the retained wad of sludge so that when it is flung from the bucket by centrifugal force it will have been raised above the level of the upper rim of the bowl 12 and its wad of sludge will be literally thrown out of the bowl and over the upper rim thereof where it will impact against the aforementioned apron 44 which is positioned outwards of the bowl.

Accordingly, the annular bowl cover plate constitutes, in effect, a sludge deck across which the elevated wads of sludge are thrown radially outwards from the raised buckets when the latter are in their inside ecliptic positions. This deck-forming cover plate 120, in combination with a circular horizontal confining wall 170 immediately thereabove, defines a plenum passage 173 (see FIG. 4) for the outwardly moving sludge in wad form. This wall 170 constitutes an element of a rotating inverted panlike structure which includes the aforementioned sludgecollecting apron 44 and the nature of which will be set forth presently.

Referring now to FIGS. 4 and 10 of the drawings, each of the two bucket turntables 34 has associated with it preferably eight buckets 30 and is in the form of a relatively thick circular plate 174 in the periphery of which there are provided eight rectangular cut-outs or recesses 176, there being one recess for each of the eight buckets 30. Each bucket 30 includes a bucket section proper (see also FIGS. 12 to 17, inclusive) and a rectangular shank portion 182, the latter fitting loosely within one of the recesses 176 and being captured therein by means of a horizontally extending transverse pivot pin 184 the ends of which are suitably rotatably mounted in oppositely disposed sockets in the side of the associated recess 176.

Each bucket section proper 181) is of rectangular box-like configuration and includes an outside side wall 186, an inside wall 188, a rear wall 190, and a bottom wall 192. The forward and top sides of each bucket 30 are open. The bucket turntables 34 are adapted to rotate in the clockwise direction indicated by the arrow in FIG. 10 and the leading edges of both the outside wall 186 and the bottom wall 192 of each bucket 30 are of knife edge construction as clearly shown in FIGS. 10 and 12 to 17, inclusive.

It should be borne in mind throughout a reading of this description that the turntables 34, although being capable of rotation about the axes of their respective central shafts 162, are movable bodily at an extremely high rate of speed in orbital fashion about the vertical axis of the central shaft 26 and, therefore, they are subject to a large magnitude of centrifugal force at all times, this force extending diametrically across the bucket turntables 34 and away from the centralshaft 26. The centrifugal force which is generated incident to individual rotation of the turntables is negligible and the urge is for every particle of solids which is contained in a given bucket 30 to be flung radially outwardly of the bowl 12. Bearing this in mind, it will be appreciated that as each bucket 30 advances in tangential fashion through the solids which have been elevated by the sludge plows 42 to bucket level, it will pick up a quantity of the sludge. Continued rotation of the associated turntable 34 during its circumferential movement bodily around the periphery of the bowl 12 will effect a direction change so that the bucket will reverse its direction with the result that its open leading side will ultimately face radially outwards of the bowl at such time as the bucket arrives at its inside ecliptic position. However, during the time that the bucket approaches its inside ecliptic position, it will encounter one of the aforementioned cam surfaces 40 (see FIGS. 4 and 8) and move to its fully raised position. Each cam surface 40 is provided on a cam member 200 (see FIGS. 4, 8 and 9) which is secured by horizontal bolts 202 to an L-shaped holding bracket 204. The latter, in turn, is fastened by vertical bolts 206 to a turret-like structure 208 which is secured by vertical bolts 210 to the cam plate 140 of the bucket carriage 32.

The sequence of bucket-raising and bucket-lowering operations is somewhat schematically illustrated in FIGS. 12 to 17, inclusive. In FIGS. 12 and 13, one of the buckets 30 is shown as it enters upon the associated fixed cam surface 40, the rear wall 192 of the bucket riding upwardly on such surface so as to swing the bucket upwardly about the axis of its pivot pin 184.

In FIGS. 14 and 15 of the drawings, the illustrated bucket is shown as having arrived at the uppermost point on the associated cam surface 40, the cam member 200 being so positioned that this takes place at the precise moment when the bucket arrives at its inside ecliptic position with respect to the shafts 162 and 26 as shown in FIG. 4. In this inside ecliptic position of the bucket, the prevailing centrifugal force acting on the illustrated bucket will cause the latter to be flung bodily in an outward direction relatively to the bowl and the bucket will leave the cam surface and move to the upright dotted-line position in which it is shown in FIG. 15. Since an open side of the bucket is at this time facing radially outwards, the wad of sludge which is contained within the bucket will be flung radially outwards as previously set forth with the result that it will pass radially over the bowl cover plate 120 (see FIG. 4) and beneath the ceiling plate 22 and against the slowly rotating sludge collection wall or apron 44 (see FIGS. 2 and 3).

In FIGS. 12 and 13 of the drawings, the manner in which the illustrated bucket 30 is restored to its lowered sludge-scooping position after it has moved beyond its inside ecliptic position is shown. Because of the fact that centrifugal force incident to the high speed of rotation of the bowl 12 and all of its adjuncts is at all times impressed upon the bucket, the latter will move away from the associated cam surface 40 and enter into engagement with the aforementioned associated cam surface 41, this latter surface being provided on the cam plate 140 by reason of the provision of a relatively large D-shaped relief opening 212 (see FIG. 6) which is cut in the plate 140. The inside edge of the relief opening which is illustrated in FIG. 6, i.e., the edge which is remote from the central shaft 26, is curved and slanted to the proper contour so that as any of the buckets 30 encounters the cam surface 41 the shank portion 182 of the bucket will ride on such surface as clearly shown in FIG. 17. Although the rear wall 190 of the illustrated bucket will oppose the associated cam surface 40, the centrifugal force acting on the bucket will maintain the bucket and surface slightly separated.

It is, of course, to be understood that the cam plate 140 has two D-shaped relief openings and they are disposed one diametrically opposite the other.

It will be understood, of course, that although the scooping action and the direction-reversing operation of only one bucket 30 has been described above, the same scopping and reversal of each of the eight buckets in each of the two series of buckets will be the same. Thus, during normal operation of the present centrifugal separator, the sludge ring or sea] 20 (see FIG. 4) will repeatedly be operated upon by the various buckets at sixteen locations around the periphery of the bucket carriage 32 and, as a consequence, a relatively large quantity of the sludge will be transferred by the buckets 30 from the sludge ring to the collection wall or apron 44. Actually, with the bowl rotating at a speed of 3,000 rpm. and the turntables 34 exceeding this speed, and with certain gear ratios being maintained as will be described presently in connection with FIG. 11, each bucket will traverse the sludge seal 20 in excess of two times for each rotation of the central shaft 26 and there will be in excess of sixty-four withdrawals of sludge from the sludge seal each minute of normal or contemplated operation of the separator.

THE SEPARATOR BOWL AND BUCKET CARRIAGE POWER TRAINS (BOWL DRIVE) Referring now to FIGS. 1, 2, 3 and 11, the aforementioned motor mount which is supported on the angle pieces 76 and 78 of the framework of the separator serves adjustably to support an electric motor M1 by means of which the bowl l2 and all of its relatively rotatable adjuncts are driven. The motor M1 is provided with a casing 220 and embodies a vertically extending rotatable output shaft 222 (see FIGS. 1 and 3) which projects downwards from the casing 220 and is driven by an armature (not shown) when the motor M1 is energized. The casing 220 embodies a laterally extending motor base 223 (see FIG. 3) the upper portion of which is secured by horizontal bolts 224 to a slide member 225. The latter has at its ends bearing sleeves 226 which slide on a horizontally extending guide rod 228, the opposite ends of which are supported in anchor blocks 230 on the upper ends of the angle pieces 76 and 78 (see FIG. 1). A pair of bearing blocks 232 are mounted on said angle pieces of the separator framework a comparatively small distance below the anchor blocks 230 and serve rotatably to support therebetween a horizontally extending threaded shaft 234. The latter passes through a pair of internally-threaded block-like lugs 236 which are formed on the lower portion of the base 223 of the motor M1. The shaft 234 projects rearwardly beyond the angle piece 76 of the framework and carries a manipulating crank 238. From the above description, it will be apparent that upon turning of the crank 238 in one direction or the other, the motor Ml will be shifted horizontally and in a longitudinal direction with respect to the separator framework for motor speed-change purposes as will be described presently.

As best illustrated in FIGS. 1 and 11, the motor M1 is adapted to transmit power to the central drive shaft 26 through the medium of a Reeves drive mechanism 240 embodying a belt and pulley assembly 242. Such assembly consists of a horizontally extending endless drive belt 243, a split spring-biased drive pulley 244, and a flat-faced driven pulley 246, the former puiley being secured on the lower end of the motor drive shaft 222 and the latter pulley being mounted on the lower end of a vertically extending jack shaft 248 (see FIG. 1). The ends of said jack shaft are rotatably mounted in uper and lower bearings 250 and 252 respectively, and these bearings are supported on respective crossbars 254 and 256 which extend between and are welded or otherwise fixedly connected to the lower end regions of the channel members 62. The jack shaft 248 has fixedly mounted on its central portion a multiple groove drive pulley 260, and a series of horizontally extending endless belts 262 pass around the pulley 260 and also around a similar driven pulley 264 on the lower end of the central drive shaft 26. From the foregoing description, it will be apparent that by rotating the crank 238 in one direction or the other, the longitudinal position of the motor MI may be varied to vary the drive ratio between the output shaft 222 of the electric motor M1 and the central shaft 26 for speedchange purposes.

Since the separator bowl 12 is bolted directly to the central shaft 26 are previously set forth, it is obvious that the bowl will rotate in unison with such shaft. Also, as previously described, rotation of the bowl 12 will effect rotation of the lower slurry deck plate 16, the upper ceiling plate 22, the sun gear 126, and the annular bowl cover plate 120 at a predetermined rate of speed which, as aforesaid, may be and is preferably on the order of 3,000 rpm.

(THE BUCKET CARRIAGE DRIVE) The bucket carriage 32 which includes the lower plow plate 142, the intermediate spacer plate 144, the upper cam plate 140, and the turret-like structure 208, is adapted to be rotated at a slightly different rate of speed than that of the bowl 12, preferably in the same direction and at a slightly increased rate of speed which, as heretofore stated, may be on the order of two rpm. over and above the rate of rotation of the central shaft 26 and the bowl 12. Thus, the desired speed differential between the carriage 32 and the bowl may be effected by a series of compound gears such as are disclosed in FIGS. 1, 2 and 3 and are schematically disclosed in FIG. 11, the entire series being designated by the reference numeral 270.

The central drive shaft 26 is rotatably mounted at its upper and lowerends by means of upper and lower thrust bearing assemblies 272 and 274, the bearing assembly 272 being secured by bolts 276 to the bottom plate 70 of the superstructure 66, and the bearing assembly 274 being secured by bolts 278 to a horizontal shelf support 280 which is welded or otherwise fixedly secured to the angle pieces 60 and the channel members 62 of the separator framework.

The central shaft 26 is provided at its upper end with a reduced upward extension 26a which projects upwardly above the bowl l2 and the upper region of such shaft extension carries a multiple sprocket 282 (see FIGS. 1 and 2) which, by means of a series of horizontally extending endless chains 283, drives a similar multiple sprocket 284 on a second vertically extending jacket shaft 286. The jack shaft 286 is eccentrically or laterally positioned with respect to the central shaft 26 and is rotatably mounted at its ends in upper and lower bearing assemblies 288 and 290. The latter are mounted, respectively, on the top and bottom plates 68 and of the superstructure 66 of the separator framework. The lower region of the jack shaft 286 has fixedly mounted thereon a gear 292 which meshes with a lower gear 294 on the lower end of a vertically extending third jacket shaft 296 (see FIG. 11). The upper and lower ends of the third jack shaft is supported in upper and lower bearings 297 and 299 respectively. An upper fixed gear 298 on the upper end region of the jack shaft 296 meshes with a carriage drive gear 300 which is secured by bolts 302 (see FIG. 4) to the upper end of a drive sleeve 304. The latter is loosely mounted on the intermediate portion of the central shaft 26 and has an internal bushing 305. The lower end of the drive sleeve 304 is provided with an outwardly extending bolting flange 306 which is secured by vertical bolts 308 to the cam plate of the bucket carriage 32.

While the diameters of the various gears and sprockets which are described above, and the number of teeth on the individual gears may vary, for illustrative purposes herein, the diameters of the two sprockets 282 and 2 are stated to be the same while the diameters of and the number of teeth on the gears 292 and 300 also correspond. The gear cluster on the jack shaft 296 embodying the two gears 294 and 298 constitutes a gear ratio increase unit, the diameter of and the number of teeth on the gear 298, the specific diameters and numbers of teeth being calculated according to engineering expediences so that the drive gear 300 will rotate at a speed of 2 rpm. faster than the gear 292. By such an arrangement, the aforementioned speed differential whereby the bowl will rotate at a speed of 3,000 rpm. and the bucket carriage 32 will rotate at a speed of 3,002 rpm. is effected.

TI-IE LIQUID DISCHARGE PAN AND ITS DRIVE MECHANISM The aforementioned cylindrical sludge-collecting apron 44 and the superjacent horizontal sludgeconfining wall (see FIGS. 1 to 4, inclusive) constitute an inverted pan-like sludge-collecting and discharge unit 45. The latter closely overlies the bowl l2 and encompasses the rim region of the latter as clearly shown in FIG. 1. The central shaft extension 26a projects upwardly through an opening 310 in the circular horizontal sludge-confining wall 170, and means are provided for causing the entire unit 45 to rotate at a relatively slow speed about the axis of such shaft extension. Accordingly, the aforementioned motor mount 83 embodies an electric motor M2 which is secured by horizontal bolts 312 to the transversely extending frame member 82 of the separator framework and is provided with a vertically extending output shaft 314 on the lower end of which there is fixedly mounted a multiple groove pulley 316. Horizontally extending endless belts 318 encompass the pulley 316 and also the cylindrical sludge-gathering apron 44 of the unit 45, and thus, upon energization of the motor M2, said unit will rotate at a relatively slow rate of speed, for example, on the order of from two to four rpm. The fixed scraper blades which are carried by the separator framework cooperate with the slowly rotating wall or apron 44 in such manner as to loosen the sludge which has been flung thereagainst from the various buckets 30 and the loosened sludge will then fall by gravity to a suitable sludge collection area where it may be withdrawn from the separator area by portable containers or by a moving conveying belt or the like (not shown).

The rotatable sludge-collecting and discharge unit 45 is supported from the fixed liquid-collecting and discharge pan 10 by means of three uprights 320 (see FIGS. 1, 2 and 3), the upper ends of which carry supporting rollers 322 (see FIG. 3) which rotate about horizontal axes and tractionally bear the weight of the unit 45. The uprights 320 also carry centering rollers 324 which rotate about vertical axes and serve tractionally to maintain the unit 45 in its coaxial relationship with respect to the bowl 12. The three uprights 320 are suitably mounted at their lower ends on the liquidcollecting and discharge pan 10. These uprights 320 are shown as being three in number and also serve to support the aforementioned scraper blades 46 in their 120 spaced apart circumferential relationship around the apron 44 on the inner side thereof.

OPERATION OF THE SEPARATOR In view of the relatively detailed description of the functioning of the pivoted buckets 30 incident to the relative 2 rpm. speed differential between the highspeed separator bowl 12 and the slightly higher speed bucket carriage 32, it is believed that, to avoid repetitious description, the operation of the centrifugal separator of the present invention will be readily apparent with only a brief description of the introduction of slurry into the bowl 12, the manner in which the solid constituents of such slurry are separated from the liquid constituents within the bowl, the manner in which the liquid is discharged from the bowl and thereafter collected, and the manner in which the centrifugallyseparated solids within the bowl are discharged over the bowl rim and thereafter collected.

In the operation of the particular separator constituting this invention, the slurry is pumped or fed through a lead-in conduit such as is shownat 330 in FIGS. 1 and 2 from whence it first passes or flows upwards through the slip union 132 and the central shaft bore 130 and then outwards through the radial passages 134, thus entering the bowl 12 centrally and near the upper rim thereof. As is well known in connection with practically all rotatable solid separatorbowls, drums, chambers or the like, the high speed of rotation of the bowl (which in the present instance is on the order of 3,000 rpm. as heretofore indicated) causes the solid constituents of the slurry to move toward the periphery of the bowl. Due to the fact that the lower deck plate 16 underlies the radial passages 134 while the ceiling plate 22 overlies such passages, the slurry issuing from the passages 134 does not have an opportunity to move downwardly within the bowl by gravity, but instead, it is flung radially outwardly through the slurry plenum passage 173 and directly toward the peripheral rim region of the bowl. For a short time, some ofthis slurry in its original unseparated state may pass upwardly above the ceiling plate 22, but as soon as sufficient solids have collected in the annular region around the outer edge or periphery of the ceiling plate 22 (see FIG. 4), such solids establish the annular sludge seal which holds back the liquid constituents, the latter then gradually filling the lower portion of the bowl beneath the deck plate 16 until such time as they are able to pass through the downwardly and outwardly extending sludge outlets 14. It should be borne in mind that the force of gravity has negligible effect on the slurry or on either the liquid or the solid constituents thereof. All of the material within the rotating bowl tends to move radially outwardly with great force so that the lower region of the bowl fills gradually with liquid from the bowl periphery toward the central bottom region of the bowl, this liquid assuming the form of a large-volume ring of liquid from which the liquid is forced out through the downspouts 97 via the outlets 14.

In order that the region in which the sludge seal 20 is formed shall not become clogged with solids (sludge) the three fixed scraper blades 42 loosen the sludge which collects in this region and the thus loosened sludge tends to creep upwardly through the narrow annulus which exists between the periphery of the ceiling plate 22 and the upper cylindrical rim section 86 of the bowl where it is then periodically withdrawn by the scooping action of the various buckets which move into close proximity with the peripheral region of the bowl each time their respective turtables 34 bring them to their outside ecliptic positions. Each thus filled bucket 30 then travels inwardly of the bowl incident to rotation of its associated turntable, whereupon it encounters the associated cam surface and becomes raised while at the same time undergoing a reversal of direction. At its inside ecliptic position, each bucket faces radially outwardly toward the slowly rotating apron 44 and it also assumes an elevated position wherein the contents thereof are disposed above the level of the cam plate 120 of the rotary bucket carriage 32. Centrifugal force thus acts on the contents of each bucket and the wad of sludge contained therein is flung radially outwardly over the cam plate and beneath the circular horizontal confining wall of the sludgecollection and discharge unit 45 so that it impacts against the cylindrical apron 44. Since this apron 44 is rotating at a relatively slow rate of speed under the influence of the motor M2, the fixed or stationary scraper blades 46 loosen the sludge and allow it to fall by gravity to a region of discharge.

The invention is not to be limited to the exact arrangement of parts shown in the accompanying drawings or described in this specification as various changes in the details of construction may be resorted to without departing from the spirit or scope of the invention. Therefore, only insofar as the invention is particularly pointed out in the accompanying claims is the same to be limited.

Having thus described the invention what we claim as new and desire to secure by letters patent is:

l. A centrifugal separator comprising a bowl having a dished bottom wall which slopes upwardly and terminates in an upper open circular rim, a horizontal deck plate disposed within said bowl and presenting a circular edge spaced inwardly of the bowl wall so as to define a first annulus which communicates with the bottom region of the bowl, a horizontal ceiling plate spaced upwardly from the deck plate and presenting a circular edge spaced'inwardly of the bowl wall a slight distance so as to define a second and narrow annulus which inhibits the flow of solids upwardly therethrough, means for effecting rotation of said bowl and plates in unison and at a relatively high speed about the vertical axis of the bowl whereby the solid constituents of slurry placed on a deck plate will be flung radially outwardly of the bowl between the deck and ceiling plates and establish an annular sludge seal between the ceiling plate and bowl wall while the liquid constituent of the slurry will be forced downwardly through the first annulus, a series of plows disposed within said bowl and mounted for rotation about said central axis in the vicinity of the sludge seal and effective upon rotation thereof to move circumferentially around the bowl wall and loosen the sludge for upward movement through said second annulus, means disposed immediately above said ceiling plate for withdrawing wads of the thus loosened sludge from the vicinity of said second annulus, conducting them inwardly of the bowl,

raising them above the level of the bowl rim, and releasing them for outward radial flinging movement under the influence of centrifugal force over the upper rim of the bowl, there being a liquid outlet in the bottom region of said bowl wall in order to effect discharge of the liquid constituent.

2. A centrifugal separator as set forth in claim 1 and including, additionally, a sludge-collector wall encompassing the rim of said bowl and upon which the sludge which is flung radially over'the rim of the bowl collects due to impact thereagainst, a scraper blade adapted to traverse said collector wall for sludge removal purposes, and means establishing relative circumferential movement between the scraper blade and collector wall.

3. A centrifugal separator as set forth in claim 2 and wherein the collector wall is generally cylindrical and concentric with the axis of the bowl, the scraper blade is fixed, and the means for establishing relative circumferential movement between the scraper blade and collector wall comprises power means for rotating the collector wall at a relatively low speed.

4. A centrifugal separator as set forth in claim 3 and wherein said power means is independent of the means for effecting rotation of the bowl.

5. A centrifugal separator as set forth in claim 1 and wherein the means for effecting rotation of the bowl and plates comprises a central shaft which passes vertically upwardly through the central portions of the bowl wall and plates in sealing relationship and to which said bowl and plates are fixedlyv secured.

6. A centrifugal separator as set forth in claim 5 and wherein said central shaftis provided with an axial bore having at least one radial passage extending therefrom and establishing communication between the bore and the space between said deck and ceiling plates, and means are provided for supplying slurry to the bore for deposition on said deck plate in the central region of the bowl via the radial passage.

7. A centrifugal separator as set forth in claim 1 and wherein the means for withdrawing wads of sludge from the vicinity of said second annulus comprises a circular series of circumferentially spaced open-sided buckets disposed within the bowl for orbital movement about the axis of the bowl at a rate of speed slightly different from the speed of rotation of the bowl and for rotation about its own axis of orbital movement, whereby the buckets thereof assume outside and inside ecliptic positions with respect to the axis of the bowl and orbital axis of the series, means for effecting rota-- becoming directionally reversed and elevated above the level of the bowl rim whereby the gathered wads of sludge will be flung radially outwardly over said rim to a region of discharge.

8. A centrifugal separator adapted to remove solids from slurry and comprising a rotatable bowl having a dished wall which slopes progressively upwardly and outwardly and terminates in an open circular rim, means for rotating said bowl about a vertical axis at relatively high speed to the end that slurry deposited within the bowl will be flung radially outwardly by centrifugal force and the solids therein cause to settle on said wall in the vicinity of said circular rim in the form of an annulus of sludge while liquid will collect in the lower central region of the bowl, a rotatable bucket carriage disposed in the upper region of the bowl and rotatable about said axis, a plurality of turntables eccentrically and rotatably mounted on said carriage for rotation about respective vertical axes and for orbiting movement about the axis of the turntable, a plurality of open-sided sludge-receiving buckets movably mounted on the periphery of each turntable whereby upon rotation of the turntables said buckets will move through outside and inside ecliptic positions with respect to the axes of the turntables and carriage means for rotating said carriage'at a speed slightly greater than that of the bowl, means for rotating said turntables about their respective axes at a relatively low speed, said buckets during passage through their outside ecliptic positions moving in tangential fashion through said sludge annulus and presenting their open sides in a leading direction so as to gather wads of sludge from said annulus, and during passage through their inside ecliptic positions becoming directionally reversed and elevated above the level of the bowl rim whereby the gathered wads of sludge will be flung radially outwardly over said rim to a region of discharge, there being a liquid outlet in the bottom region of said bowl wall for permitting liquid discharge.

9. A centrifugal separator as set forth in claim 8 and including, additionally, a rotatable cylindrical collector wall concentric with the axis of said bowl, encompassing the rim region of the bowl for impact reception thereagainst of the sludge which is flung outwardly over the rim of the bowl, means for rotating said collector wall at a relatively slow rate of speed, and a fixed scraper blade adapted to traverse said collector wall for sludge-removal purposes.

10. A centrifugal separator as set forth in claim 8 and wherein the means for rotating the carriage at a speed greater than that of the bowl comprises differential gearing effective between the separator bowl and the carriage.

l l. A centrifugal separator as set forth in claim 8 and wherein said sludge-receiving buckets are pivotally connected to their respective turntables for individual swinging movement between lowered positions wherein the buckets lie below the level of the bowl rim andelevated positions wherein they are disposed above such level, and cam means are provided for moving said buckets to their directionally reversed elevated positions during movement thereof from their outside to their inside ecliptic positions.

12. A centrifugal separator as set forth in claim 11 and wherein the cam means comprises a cam surface associated with each turntable, fixedly disposed on said carriage, and engageable with successive buckets as they approach their inside ecliptic positions.

13. A centrifugal separator as set forth in claim 11 and including, additionally, cam means for restoring said buckets to their lowered positions during movement thereof from their inside to their outside ecliptic positions.

14. A centrifugal separator as set forth in claim 13 and wherein said last mentioned cam means comprises a cam surface associated with each turntable, fixedly mounted on said carriage, and engageable with successive buckets as they approach their outside ecliptic positions.

15. A centrifugal separator adapted to remove solids from slurry and comprising an upright rotatable bowl having a dished wall which slopes progressively upwardly and outwardly and terminates in an upper open circular rim, a horizontal deck plate fixedly mounted within said bowl for reception of slurry thereon and presenting a circular peripheral edge which is spaced inwardly of the bowl wall and defines, in combination therewith, a first annulus which communicates with the bottom region of the bowl, a horizontal celing plate fixedly mounted withinthe bowl, spaced upwardly from the deck plate, and presenting a circular peripheral edge which is spaced inwardly of the bowl wall and defines, in combination therewith, asecond and narrow annulus which inhibits the flow of solids upwardly above the level of said ceiling plate, means for rotating the bowl at a relatively high speed about a vertical axis whereby the solid constituents of the slurry received on said deck plate will be flung radially outwards of the bowl toward said second narrow annulus so as to establish a sludge seal therebeneath while the liquid constituent of the slurry will be forced downwardly through said first annulus into the central bottom region of the bowl, a horizontal rotatable bucket carriage disposed within said bowl immediately above said ceiling plate and substantially coextensive with the latter, means for rotating said carriage about the vertical axis of the bow] at a rate of speed slightly greater than that of the bowl, a series of plows mounted on the periphery of said carriage and projecting downwardly through said second narrow annulus for circumferential sweeping movement therearound and through the sludge seal for loosening the sludge and elevating the same through said second narrow annulus, a plurality of turntables eccentrically and rotatably mounted on said carriage for rotation about respective vertical axes and for orbiting movement about the axis of the turntable, a plurality of open-sided sludge-receiving buckets movably mounted on the periphery of each turntable whereby upon rotation of such turntable said buckets will move through outside and inside ecliptic position with respect to the axes of the turntable and carriage means for rotating said carriage at a speed slightly different from that of the carriage, and means for rotating said turntables about their respective axes at a relatively low speed, said buckets during passage through their outside ecliptic positions moving in tangential fashion through the loosened and elevated sludge and presenting their open sides in a leading direction so as to gather wads of sludge, and during passage through their inside ecliptic positions becoming directionally reversed and elevated above the level of the bowl rim whereby the gathered wads of sludge will be flung radially outwardly over said rim to a region of discharge, there being an outlet in the bottom region of said bowl wall for the discharge of the separated liquid.

16. A centrifugal separator as set forth in claim 15 and wherein said sludge-receiving buckets are pivotally connected to their respective turntables for individual swinging movement between lowered positions wherein the buckets lie below the level of the bowl rim and elevated positions wherein they are disposed above such level, and cam means are provided for moving said buckets to their directionally reversed elevated positions during movement thereof from their outside to their inside ecliptic positions.

17. A centrifugal separator as set forth in claim 16 and wherein said cam means comprises a cam surface associated with each turntable, fixedly disposed on said bowl and engageable with successive buckets as they approach their inside ecliptic positions.

18. A centrifugal separator as set forth in claim 16 and wherein additional cam means are provided for restoring said buckets to their lowered positions during movement thereof from their inside ecliptic positions to their outside ecliptic positions.

19. A centrifugal separator as set forth in claim 18 and wherein said additional cam means comprises a cam surface associated with each turntable, fixedly mounted on the bowl, and engageable with successive buckets as they approach their outside ecliptic positions.

20. A centrifugal separator as set forth in claim 15 and wherein said means for rotating the carriage at a speed greater than that of the bowl comprises differential gearing effective between the separator bowl and the carriage.

21. A centrifugal separator as set forth in claim 20 and wherein said differential gearing comprises a first jack shaft having a sprocket thereon, a sprocket effectively mounted on the bowl, a belt passing over said sprockets, a second jack shaft having a gear thereon, a gear effectively mounted on the carriage and meshing with the gear on the second jack shaft, and a pair of meshing gears on said jack shafts, said gears on the second jack shaft establishing a gear reduction ratio between the first jack shaft and the gear on said carriage.

22. A centrifugal separator as set forth in claim 15 and including, additionally, a sludge-collector wall encompassing the rim region of the bowl and upon which the sludge which is flung radially over the rim of the bowl collects due to impact thereagainst, a scraper blade adapted to traverse said collector wall for sludge removal purposes, and means establishing relative circumferential movement between the scraper blade and the collector wall.

23. A centrifugal separator as set forth in claim 22 and wherein the collector wall is generally cylindrical and concentric with the axis of the bowl, the scraper blade is fixed, and the means for establishing relative circumferential movement between the blade and wall comprises power means for rotating the collector wall at a relatively low speed.

24. A centrifugal separator as set forth in claim 15 and wherein the means for rotating said turntables about their respective axes comprises a sun gear mounted on said carriage in concentric relationship, and planet gears mounted on said platforms in concentric relationship and meshing with said sun gear.

25. A centrifugal separator as set forth in claim 24 and including, additionally, an annular cover plate secured to the upper circular rim of said dished bowl wall and projecting inwardly of the bowl immediately above said carriage.

26. A centrifugal separator as set forth in claim 25 and including, additionally, a cam surface effectively carried by said cover plate, associated with each turntable, and engageable with successive buckets as they approach their inside ecliptic positions for moving said buckets to their directionally reversed elevated positions.

27. A centrifugal separator as set forth in claim 26 and including, additionally, a second cam surface effectively carried by said cover plate, associated with each turntable, and engageable with successive buckets as they approach their outside ecliptic positions.

28. A centrifugal separator adapted to remove solids from slurry and comprising an upright rotatable bowl having a dished wall which slopes progressively upwardly and outwardly and terminates in an upper open circular rim, a horizontal plate fixedly mounted within said bowl below the level of said rim and presenting a peripheral edge which is spaced inwardly of the bowl wall and defines, in combination therewith, a narrow annulus which inhibits the flow of slurry solids upwardly above the level of said plate, means for rotating the bowl about a vertical axis at high speed whereby the solid constituents of slurry received within the bowl will be flung radially outwardly toward said annulus and establish a sludge seal therebetween while the liquid of the slurry will remain in the central region of the bowl, a plow disposed in the peripheral region of the bowl, projecting downwardly through said annulus, and effective upon circumferential travel around said peripheral region to traverse said sludge seal for loosening the sludge and effecting elevation thereof through said annulus, and means disposed immediately above said plate for withdrawing wads of the thus loosened sludge from the vicinity of the annulus, then conducting them inwardly of the bowl, then elevating them, and finally releasing them for conduction by centrifugal force radially outwardly and over the rim of said bowl, and means for effecting circumferential movement of said plow at a rate of speed slightly different from the speed of rotation of the bowl.

29. A centrifugal separator as set forth in claim 28 and wherein said means for withdrawing wads of sludge from the vicinity of said annulus comprises a circular series of circumferentially spaced, open-sided,.scooplike buckets disposed within the bowl, for orbital movement about the axis of the bowl at a rate of speed slightly different from the speed of rotation of the bowl and for rotation about its own central axis, said buckets during passage through their outside ecliptic position moving in tangential fashion into close proximity to the bowl wall and presenting their open sides in a leading direction so as to gather wads of sludge from the vicinity of said annulus, and during passage through their inside ecliptic position becoming directionally reversed so as to present their open sides radially outwardly of the bowl whereby the wads of sludge contained therein will be released.

30. A centrifugal separator as set forth in claim 28 and wherein said means for withdrawing sludge from the vicinity of said annulus and the means for effecting circumferential movement of the plow comprises a circular carriage disposed immediately above said horizontal plate and concentric with the bowl and to which the plow is fixedly secured and to which the buckets are individually pivoted for swinging movement between lowered positions below the level of said rim and raised positions above such rim.

31. A centrifugal separator as set forth in claim 30 and wherein the means for rotating the bowl comprises a central shaft which passes vertically upwardly through the bowl wall in sealing relationship and to which the bowl wall is fixedly secured, said shaft being provided with an axial bore which communicates through radial passages with the interior of the bowl in the central region thereof and immediately below said horizontal plate, and means are provided for continuously supplying slurry to said bore whereby such slurry is fed to the interior of the bowl in the central upper regions thereof via the radial passages.

32. A centrifugal separator as set forth in claim 30 and including, additionally, a circular deck plate fixedly mounted within the bowl immediately below the level of said radial passages, said deck plate presenting a peripheral edge which is spaced inwardly of the bowl wall a slight distance, said circular plates defining therebetween a plenum passage for the outward flow of slurry from said radialpassages toward said narrow annulus.

33. A centrifugal separator as set forth in claim 32 and including, additionally, a first series of spacer members interposed between and secured to said circular plates in the peripheral regions thereof and in circumferentially spaced relationship, and a second series of spacer members interposed between and secured to said deck plate and the bowl wall in the peripheral regions thereof and in circumferentially spaced relationship.

34. A centrifugal separator as set forth in claim 33 and wherein the spacer members of the first and second series are in the form of tubular sleeves which are disposed in paired end-to-end alignment, and the means for securing the spacer members to the plates and bowl wall embodies a bolt which projects axially through each pair of aligned sleeves.

35. A centrifugal separator as set forth in claim 28 and including, additionally, a rotatable cylindrical sludge-collector wall concentric with the axis of the bowl, encompassing the rim region of the bowl and against which sludge which is flung over the rim of the bowl impacts, means for rotating said collector wall about said axis of the bowl at a relatively low speed, and a fixed scraper blade positioned in close proximity tothe inside surface of said wall for sludge removal purposes.

36. A centrifugal separator as set forth in claim 35 and wherein the means for rotating said bowl comprises a central shaft which passes vertically upwardly through the bowl wall in sealing relationship and to which the bowl wall is fixedly secured, a first electric motor is operatively connected to said central shaft in driving relationship, and the means for rotating the collector wall comprises a second electric motor provided with an output shaft having a pulley thereon, and a belt encompassing said pulley and the cylindrical sludgecollector wall and in direct contact with the latter.

37. A centrifugal separator as set forth in claim 36 and wherein said central shaft has formed therein an axial bore which communicates through radial passages with the interior of the bowl, said passages opening into the interior of the bowl immediately below the level of said horizontal circular plate.

38. A centrifugal separator as set forth in claim 8 and wherein said turntables are equally and circumferentially spaced about said vertical axis in centrifugally balanced relationship.

39. A centrifugal separator as set forth in claim 38 and wherein the means for rotating said turntables comprises a planetary gear system including a sun gear coaxial with the bowl and fixedly secured thereto for rotation in unison therewith, and a planet gear on each turntable, coaxial therewith, and meshing with said sun gear.

40. A centrifugal separator as set forth in claim 8 and wherein said buckets are of scoop-like construction having leading edges which are tapered to provide sharp linear edges which cooperate with the bowl shell in loosening sludge therefrom and conducting the same to the interior of the buckets.

41. A centrifugal separator as set forth in claim and wherein said turntables are in the form of cylindrical members having inwardly extending recesses in the periphery thereof and arranged in equally and circumferentially spaced relationship, the buckets are provided with shank portions which project radially inwardly of the turntables and are normally disposed within the recesses, pivot pins project across the recesses and through the shank portions and thus pivotally connect the buckets to the turntable for swinging movement between lowered positions wherein the buckets lie substantially in the plane of the turntable and elevated positions wherein they are disposed above said plane.

42. A centrifugal separator as set forth in claim 41 and wherein cam means are fixedly mounted on the carriage in the vicinity of each turntable and engageable with the buckets thereof for swinging the latter upwardly to their raised positions during movement of the buckets toward their inside ecliptic positions.

43. A centrifugal separator as set forth in claim 42 and wherein additional cam means are fixedly mounted on the carriage in the vicinity of each turntable and engageable with the buckets thereof for swinging the latter downwardly to their lowered positions during movement of the buckets toward their outside ecliptic posi- 

1. A Centrifugal separator comprising a bowl having a dished bottom wall which slopes upwardly and terminates in an upper open circular rim, a horizontal deck plate disposed within said bowl and presenting a circular edge spaced inwardly of the bowl wall so as to define a first annulus which communicates with the bottom region of the bowl, a horizontal ceiling plate spaced upwardly from the deck plate and presenting a circular edge spaced inwardly of the bowl wall a slight distance so as to define a second and narrow annulus which inhibits the flow of solids upwardly therethrough, means for effecting rotation of said bowl and plates in unison and at a relatively high speed about the vertical axis of the bowl whereby the solid constituents of slurry placed on a deck plate will be flung radially outwardly of the bowl between the deck and ceiling plates and establish an annular sludge seal between the ceiling plate and bowl wall while the liquid constituent of the slurry will be forced downwardly through the first annulus, a series of plows disposed within said bowl and mounted for rotation about said central axis in the vicinity of the sludge seal and effective upon rotation thereof to move circumferentially around the bowl wall and loosen the sludge for upward movement through said second annulus, means disposed immediately above said ceiling plate for withdrawing wads of the thus loosened sludge from the vicinity of said second annulus, conducting them inwardly of the bowl, raising them above the level of the bowl rim, and releasing them for outward radial flinging movement under the influence of centrifugal force over the upper rim of the bowl, there being a liquid outlet in the bottom region of said bowl wall in order to effect discharge of the liquid constituent.
 2. A centrifugal separator as set forth in claim 1 and including, additionally, a sludge-collector wall encompassing the rim of said bowl and upon which the sludge which is flung radially over the rim of the bowl collects due to impact thereagainst, a scraper blade adapted to traverse said collector wall for sludge removal purposes, and means establishing relative circumferential movement between the scraper blade and collector wall.
 3. A centrifugal separator as set forth in claim 2 and wherein the collector wall is generally cylindrical and concentric with the axis of the bowl, the scraper blade is fixed, and the means for establishing relative circumferential movement between the scraper blade and collector wall comprises power means for rotating the collector wall at a relatively low speed.
 4. A centrifugal separator as set forth in claim 3 and wherein said power means is independent of the means for effecting rotation of the bowl.
 5. A centrifugal separator as set forth in claim 1 and wherein the means for effecting rotation of the bowl and plates comprises a central shaft which passes vertically upwardly through the central portions of the bowl wall and plates in sealing relationship and to which said bowl and plates are fixedly secured.
 6. A centrifugal separator as set forth in claim 5 and wherein said central shaft is provided with an axial bore having at least one radial passage extending therefrom and establishing communication between the bore and the space between said deck and ceiling plates, and means are provided for supplying slurry to the bore for deposition on said deck plate in the central region of the bowl via the radial passage.
 7. A centrifugal separator as set forth in claim 1 and wherein the means for withdrawing wads of sludge from the vicinity of said second annulus comprises a circular series of circumferentially spaced open-sided buckets disposed within the bowl for orbital movement about the axis of the bowl at a rate of speed slightly different from the speed of rotation of the bowl and for rotation about its own axis of orbital movement, whereby the buckets thereof assume outside and inside ecliptic positions with respect to the axis of the bowl and orbital axis of the serieS, means for effecting rotation of said series of buckets at a relatively slow rate of speed, said buckets during passage through their outside ecliptic positions moving in tangential fashion into close proximity to said bowl wall and presenting their open sides in a leading direction so as to gather wads of sludge from the vicinity of said second annulus, and during passage through their inside ecliptic positions becoming directionally reversed and elevated above the level of the bowl rim whereby the gathered wads of sludge will be flung radially outwardly over said rim to a region of discharge.
 8. A centrifugal separator adapted to remove solids from slurry and comprising a rotatable bowl having a dished wall which slopes progressively upwardly and outwardly and terminates in an open circular rim, means for rotating said bowl about a vertical axis at relatively high speed to the end that slurry deposited within the bowl will be flung radially outwardly by centrifugal force and the solids therein cause to settle on said wall in the vicinity of said circular rim in the form of an annulus of sludge while liquid will collect in the lower central region of the bowl, a rotatable bucket carriage disposed in the upper region of the bowl and rotatable about said axis, a plurality of turntables eccentrically and rotatably mounted on said carriage for rotation about respective vertical axes and for orbiting movement about the axis of the turntable, a plurality of open-sided sludge-receiving buckets movably mounted on the periphery of each turntable whereby upon rotation of the turntables said buckets will move through outside and inside ecliptic positions with respect to the axes of the turntables and carriage means for rotating said carriage at a speed slightly greater than that of the bowl, means for rotating said turntables about their respective axes at a relatively low speed, said buckets during passage through their outside ecliptic positions moving in tangential fashion through said sludge annulus and presenting their open sides in a leading direction so as to gather wads of sludge from said annulus, and during passage through their inside ecliptic positions becoming directionally reversed and elevated above the level of the bowl rim whereby the gathered wads of sludge will be flung radially outwardly over said rim to a region of discharge, there being a liquid outlet in the bottom region of said bowl wall for permitting liquid discharge.
 9. A centrifugal separator as set forth in claim 8 and including, additionally, a rotatable cylindrical collector wall concentric with the axis of said bowl, encompassing the rim region of the bowl for impact reception thereagainst of the sludge which is flung outwardly over the rim of the bowl, means for rotating said collector wall at a relatively slow rate of speed, and a fixed scraper blade adapted to traverse said collector wall for sludge-removal purposes.
 10. A centrifugal separator as set forth in claim 8 and wherein the means for rotating the carriage at a speed greater than that of the bowl comprises differential gearing effective between the separator bowl and the carriage.
 11. A centrifugal separator as set forth in claim 8 and wherein said sludge-receiving buckets are pivotally connected to their respective turntables for individual swinging movement between lowered positions wherein the buckets lie below the level of the bowl rim and elevated positions wherein they are disposed above such level, and cam means are provided for moving said buckets to their directionally reversed elevated positions during movement thereof from their outside to their inside ecliptic positions.
 12. A centrifugal separator as set forth in claim 11 and wherein the cam means comprises a cam surface associated with each turntable, fixedly disposed on said carriage, and engageable with successive buckets as they approach their inside ecliptic positions.
 13. A centrifugal separator as set forth in claim 11 and including, additionally, cam means for restoring said buckets to their lowered positions during movement thereof from their inside to their outside ecliptic positions.
 14. A centrifugal separator as set forth in claim 13 and wherein said last mentioned cam means comprises a cam surface associated with each turntable, fixedly mounted on said carriage, and engageable with successive buckets as they approach their outside ecliptic positions.
 15. A centrifugal separator adapted to remove solids from slurry and comprising an upright rotatable bowl having a dished wall which slopes progressively upwardly and outwardly and terminates in an upper open circular rim, a horizontal deck plate fixedly mounted within said bowl for reception of slurry thereon and presenting a circular peripheral edge which is spaced inwardly of the bowl wall and defines, in combination therewith, a first annulus which communicates with the bottom region of the bowl, a horizontal celing plate fixedly mounted within the bowl, spaced upwardly from the deck plate, and presenting a circular peripheral edge which is spaced inwardly of the bowl wall and defines, in combination therewith, a second and narrow annulus which inhibits the flow of solids upwardly above the level of said ceiling plate, means for rotating the bowl at a relatively high speed about a vertical axis whereby the solid constituents of the slurry received on said deck plate will be flung radially outwards of the bowl toward said second narrow annulus so as to establish a sludge seal therebeneath while the liquid constituent of the slurry will be forced downwardly through said first annulus into the central bottom region of the bowl, a horizontal rotatable bucket carriage disposed within said bowl immediately above said ceiling plate and substantially coextensive with the latter, means for rotating said carriage about the vertical axis of the bowl at a rate of speed slightly greater than that of the bowl, a series of plows mounted on the periphery of said carriage and projecting downwardly through said second narrow annulus for circumferential sweeping movement therearound and through the sludge seal for loosening the sludge and elevating the same through said second narrow annulus, a plurality of turntables eccentrically and rotatably mounted on said carriage for rotation about respective vertical axes and for orbiting movement about the axis of the turntable, a plurality of open-sided sludge-receiving buckets movably mounted on the periphery of each turntable whereby upon rotation of such turntable said buckets will move through outside and inside ecliptic position with respect to the axes of the turntable and carriage means for rotating said carriage at a speed slightly different from that of the carriage, and means for rotating said turntables about their respective axes at a relatively low speed, said buckets during passage through their outside ecliptic positions moving in tangential fashion through the loosened and elevated sludge and presenting their open sides in a leading direction so as to gather wads of sludge, and during passage through their inside ecliptic positions becoming directionally reversed and elevated above the level of the bowl rim whereby the gathered wads of sludge will be flung radially outwardly over said rim to a region of discharge, there being an outlet in the bottom region of said bowl wall for the discharge of the separated liquid.
 16. A centrifugal separator as set forth in claim 15 and wherein said sludge-receiving buckets are pivotally connected to their respective turntables for individual swinging movement between lowered positions wherein the buckets lie below the level of the bowl rim and elevated positions wherein they are disposed above such level, and cam means are provided for moving said buckets to their directionally reversed elevated positions during movement thereof from their outside to their inside ecliptic positions.
 17. A centrifugal separator as set forth in claim 16 and wherein said cam means comprises a caM surface associated with each turntable, fixedly disposed on said bowl and engageable with successive buckets as they approach their inside ecliptic positions.
 18. A centrifugal separator as set forth in claim 16 and wherein additional cam means are provided for restoring said buckets to their lowered positions during movement thereof from their inside ecliptic positions to their outside ecliptic positions.
 19. A centrifugal separator as set forth in claim 18 and wherein said additional cam means comprises a cam surface associated with each turntable, fixedly mounted on the bowl, and engageable with successive buckets as they approach their outside ecliptic positions.
 20. A centrifugal separator as set forth in claim 15 and wherein said means for rotating the carriage at a speed greater than that of the bowl comprises differential gearing effective between the separator bowl and the carriage.
 21. A centrifugal separator as set forth in claim 20 and wherein said differential gearing comprises a first jack shaft having a sprocket thereon, a sprocket effectively mounted on the bowl, a belt passing over said sprockets, a second jack shaft having a gear thereon, a gear effectively mounted on the carriage and meshing with the gear on the second jack shaft, and a pair of meshing gears on said jack shafts, said gears on the second jack shaft establishing a gear reduction ratio between the first jack shaft and the gear on said carriage.
 22. A centrifugal separator as set forth in claim 15 and including, additionally, a sludge-collector wall encompassing the rim region of the bowl and upon which the sludge which is flung radially over the rim of the bowl collects due to impact thereagainst, a scraper blade adapted to traverse said collector wall for sludge removal purposes, and means establishing relative circumferential movement between the scraper blade and the collector wall.
 23. A centrifugal separator as set forth in claim 22 and wherein the collector wall is generally cylindrical and concentric with the axis of the bowl, the scraper blade is fixed, and the means for establishing relative circumferential movement between the blade and wall comprises power means for rotating the collector wall at a relatively low speed.
 24. A centrifugal separator as set forth in claim 15 and wherein the means for rotating said turntables about their respective axes comprises a sun gear mounted on said carriage in concentric relationship, and planet gears mounted on said platforms in concentric relationship and meshing with said sun gear.
 25. A centrifugal separator as set forth in claim 24 and including, additionally, an annular cover plate secured to the upper circular rim of said dished bowl wall and projecting inwardly of the bowl immediately above said carriage.
 26. A centrifugal separator as set forth in claim 25 and including, additionally, a cam surface effectively carried by said cover plate, associated with each turntable, and engageable with successive buckets as they approach their inside ecliptic positions for moving said buckets to their directionally reversed elevated positions.
 27. A centrifugal separator as set forth in claim 26 and including, additionally, a second cam surface effectively carried by said cover plate, associated with each turntable, and engageable with successive buckets as they approach their outside ecliptic positions.
 28. A centrifugal separator adapted to remove solids from slurry and comprising an upright rotatable bowl having a dished wall which slopes progressively upwardly and outwardly and terminates in an upper open circular rim, a horizontal plate fixedly mounted within said bowl below the level of said rim and presenting a peripheral edge which is spaced inwardly of the bowl wall and defines, in combination therewith, a narrow annulus which inhibits the flow of slurry solids upwardly above the level of said plate, means for rotating the bowl about a vertical axis at high speed whereby the solid constituents of slurry rEceived within the bowl will be flung radially outwardly toward said annulus and establish a sludge seal therebetween while the liquid of the slurry will remain in the central region of the bowl, a plow disposed in the peripheral region of the bowl, projecting downwardly through said annulus, and effective upon circumferential travel around said peripheral region to traverse said sludge seal for loosening the sludge and effecting elevation thereof through said annulus, and means disposed immediately above said plate for withdrawing wads of the thus loosened sludge from the vicinity of the annulus, then conducting them inwardly of the bowl, then elevating them, and finally releasing them for conduction by centrifugal force radially outwardly and over the rim of said bowl, and means for effecting circumferential movement of said plow at a rate of speed slightly different from the speed of rotation of the bowl.
 29. A centrifugal separator as set forth in claim 28 and wherein said means for withdrawing wads of sludge from the vicinity of said annulus comprises a circular series of circumferentially spaced, open-sided, scoop-like buckets disposed within the bowl for orbital movement about the axis of the bowl at a rate of speed slightly different from the speed of rotation of the bowl and for rotation about its own central axis, said buckets during passage through their outside ecliptic position moving in tangential fashion into close proximity to the bowl wall and presenting their open sides in a leading direction so as to gather wads of sludge from the vicinity of said annulus, and during passage through their inside ecliptic position becoming directionally reversed so as to present their open sides radially outwardly of the bowl whereby the wads of sludge contained therein will be released.
 30. A centrifugal separator as set forth in claim 28 and wherein said means for withdrawing sludge from the vicinity of said annulus and the means for effecting circumferential movement of the plow comprises a circular carriage disposed immediately above said horizontal plate and concentric with the bowl and to which the plow is fixedly secured and to which the buckets are individually pivoted for swinging movement between lowered positions below the level of said rim and raised positions above such rim.
 31. A centrifugal separator as set forth in claim 30 and wherein the means for rotating the bowl comprises a central shaft which passes vertically upwardly through the bowl wall in sealing relationship and to which the bowl wall is fixedly secured, said shaft being provided with an axial bore which communicates through radial passages with the interior of the bowl in the central region thereof and immediately below said horizontal plate, and means are provided for continuously supplying slurry to said bore whereby such slurry is fed to the interior of the bowl in the central upper regions thereof via the radial passages.
 32. A centrifugal separator as set forth in claim 30 and including, additionally, a circular deck plate fixedly mounted within the bowl immediately below the level of said radial passages, said deck plate presenting a peripheral edge which is spaced inwardly of the bowl wall a slight distance, said circular plates defining therebetween a plenum passage for the outward flow of slurry from said radial passages toward said narrow annulus.
 33. A centrifugal separator as set forth in claim 32 and including, additionally, a first series of spacer members interposed between and secured to said circular plates in the peripheral regions thereof and in circumferentially spaced relationship, and a second series of spacer members interposed between and secured to said deck plate and the bowl wall in the peripheral regions thereof and in circumferentially spaced relationship.
 34. A centrifugal separator as set forth in claim 33 and wherein the spacer members of the first and second series are in the form of tubular sleeves which are disposed in paired end-to-end alignmEnt, and the means for securing the spacer members to the plates and bowl wall embodies a bolt which projects axially through each pair of aligned sleeves.
 35. A centrifugal separator as set forth in claim 28 and including, additionally, a rotatable cylindrical sludge-collector wall concentric with the axis of the bowl, encompassing the rim region of the bowl and against which sludge which is flung over the rim of the bowl impacts, means for rotating said collector wall about said axis of the bowl at a relatively low speed, and a fixed scraper blade positioned in close proximity to the inside surface of said wall for sludge removal purposes.
 36. A centrifugal separator as set forth in claim 35 and wherein the means for rotating said bowl comprises a central shaft which passes vertically upwardly through the bowl wall in sealing relationship and to which the bowl wall is fixedly secured, a first electric motor is operatively connected to said central shaft in driving relationship, and the means for rotating the collector wall comprises a second electric motor provided with an output shaft having a pulley thereon, and a belt encompassing said pulley and the cylindrical sludge-collector wall and in direct contact with the latter.
 37. A centrifugal separator as set forth in claim 36 and wherein said central shaft has formed therein an axial bore which communicates through radial passages with the interior of the bowl, said passages opening into the interior of the bowl immediately below the level of said horizontal circular plate.
 38. A centrifugal separator as set forth in claim 8 and wherein said turntables are equally and circumferentially spaced about said vertical axis in centrifugally balanced relationship.
 39. A centrifugal separator as set forth in claim 38 and wherein the means for rotating said turntables comprises a planetary gear system including a sun gear coaxial with the bowl and fixedly secured thereto for rotation in unison therewith, and a planet gear on each turntable, coaxial therewith, and meshing with said sun gear.
 40. A centrifugal separator as set forth in claim 8 and wherein said buckets are of scoop-like construction having leading edges which are tapered to provide sharp linear edges which cooperate with the bowl shell in loosening sludge therefrom and conducting the same to the interior of the buckets.
 41. A centrifugal separator as set forth in claim 15 and wherein said turntables are in the form of cylindrical members having inwardly extending recesses in the periphery thereof and arranged in equally and circumferentially spaced relationship, the buckets are provided with shank portions which project radially inwardly of the turntables and are normally disposed within the recesses, pivot pins project across the recesses and through the shank portions and thus pivotally connect the buckets to the turntable for swinging movement between lowered positions wherein the buckets lie substantially in the plane of the turntable and elevated positions wherein they are disposed above said plane.
 42. A centrifugal separator as set forth in claim 41 and wherein cam means are fixedly mounted on the carriage in the vicinity of each turntable and engageable with the buckets thereof for swinging the latter upwardly to their raised positions during movement of the buckets toward their inside ecliptic positions.
 43. A centrifugal separator as set forth in claim 42 and wherein additional cam means are fixedly mounted on the carriage in the vicinity of each turntable and engageable with the buckets thereof for swinging the latter downwardly to their lowered positions during movement of the buckets toward their outside ecliptic positions. 